// GenericsNote: Converted.
/*
 *  Copyright 2002-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.jivesoftware.smack.util.collections;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

/**
 * A <code>Map</code> implementation that allows mappings to be removed by the
 * garbage collector.
 * <p/>
 * When you construct a <code>ReferenceMap</code>, you can specify what kind of
 * references are used to store the map's keys and values. If non-hard
 * references are used, then the garbage collector can remove mappings if a key
 * or value becomes unreachable, or if the JVM's memory is running low. For
 * information on how the different reference types behave, see
 * {@link java.lang.ref.Reference}.
 * <p/>
 * Different types of references can be specified for keys and values. The keys
 * can be configured to be weak but the values hard, in which case this class
 * will behave like a <a
 * href="http://java.sun.com/j2se/1.4/docs/api/java/util/WeakHashMap.html">
 * <code>WeakHashMap</code></a>. However, you can also specify hard keys and
 * weak values, or any other combination. The default constructor uses hard keys
 * and soft values, providing a memory-sensitive cache.
 * <p/>
 * This map is similar to ReferenceIdentityMap. It differs in that keys and
 * values in this class are compared using <code>equals()</code>.
 * <p/>
 * This {@link java.util.Map} implementation does <i>not</i> allow null
 * elements. Attempting to add a null key or value to the map will raise a
 * <code>NullPointerException</code>.
 * <p/>
 * This implementation is not synchronized. You can use
 * {@link java.util.Collections#synchronizedMap} to provide synchronized access
 * to a <code>ReferenceMap</code>. Remember that synchronization will not stop
 * the garbage collecter removing entries.
 * <p/>
 * All the available iterators can be reset back to the start by casting to
 * <code>ResettableIterator</code> and calling <code>reset()</code>.
 * <p/>
 * NOTE: As from Commons Collections 3.1 this map extends
 * <code>AbstractReferenceMap</code> (previously it extended AbstractMap). As a
 * result, the implementation is now extensible and provides a
 * <code>MapIterator</code>.
 * 
 * @author Paul Jack
 * @author Matt Hall, John Watkinson, Stephen Colebourne
 * @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:32 $
 * @see java.lang.ref.Reference
 * @since Commons Collections 3.0 (previously in main package v2.1)
 */
public class ReferenceMap<K, V> extends AbstractReferenceMap<K, V> implements
		Serializable {

	/**
	 * Serialization version
	 */
	private static final long serialVersionUID = 1555089888138299607L;

	/**
	 * Constructs a new <code>ReferenceMap</code> that will use hard references
	 * to keys and soft references to values.
	 */
	public ReferenceMap() {
		super(HARD, SOFT, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, false);
	}

	/**
	 * Constructs a new <code>ReferenceMap</code> that will use the specified
	 * types of references.
	 * 
	 * @param keyType
	 *            the type of reference to use for keys; must be {@link #HARD},
	 *            {@link #SOFT}, {@link #WEAK}
	 * @param valueType
	 *            the type of reference to use for values; must be {@link #HARD}
	 *            , {@link #SOFT}, {@link #WEAK}
	 */
	public ReferenceMap(int keyType, int valueType) {
		super(keyType, valueType, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, false);
	}

	/**
	 * Constructs a new <code>ReferenceMap</code> that will use the specified
	 * types of references.
	 * 
	 * @param keyType
	 *            the type of reference to use for keys; must be {@link #HARD},
	 *            {@link #SOFT}, {@link #WEAK}
	 * @param valueType
	 *            the type of reference to use for values; must be {@link #HARD}
	 *            , {@link #SOFT}, {@link #WEAK}
	 * @param purgeValues
	 *            should the value be automatically purged when the key is
	 *            garbage collected
	 */
	public ReferenceMap(int keyType, int valueType, boolean purgeValues) {
		super(keyType, valueType, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR,
				purgeValues);
	}

	/**
	 * Constructs a new <code>ReferenceMap</code> with the specified reference
	 * types, load factor and initial capacity.
	 * 
	 * @param keyType
	 *            the type of reference to use for keys; must be {@link #HARD},
	 *            {@link #SOFT}, {@link #WEAK}
	 * @param valueType
	 *            the type of reference to use for values; must be {@link #HARD}
	 *            , {@link #SOFT}, {@link #WEAK}
	 * @param capacity
	 *            the initial capacity for the map
	 * @param loadFactor
	 *            the load factor for the map
	 */
	public ReferenceMap(int keyType, int valueType, int capacity,
			float loadFactor) {
		super(keyType, valueType, capacity, loadFactor, false);
	}

	/**
	 * Constructs a new <code>ReferenceMap</code> with the specified reference
	 * types, load factor and initial capacity.
	 * 
	 * @param keyType
	 *            the type of reference to use for keys; must be {@link #HARD},
	 *            {@link #SOFT}, {@link #WEAK}
	 * @param valueType
	 *            the type of reference to use for values; must be {@link #HARD}
	 *            , {@link #SOFT}, {@link #WEAK}
	 * @param capacity
	 *            the initial capacity for the map
	 * @param loadFactor
	 *            the load factor for the map
	 * @param purgeValues
	 *            should the value be automatically purged when the key is
	 *            garbage collected
	 */
	public ReferenceMap(int keyType, int valueType, int capacity,
			float loadFactor, boolean purgeValues) {
		super(keyType, valueType, capacity, loadFactor, purgeValues);
	}

	// -----------------------------------------------------------------------
	/**
	 * Write the map out using a custom routine.
	 */
	private void writeObject(ObjectOutputStream out) throws IOException {
		out.defaultWriteObject();
		doWriteObject(out);
	}

	/**
	 * Read the map in using a custom routine.
	 */
	private void readObject(ObjectInputStream in) throws IOException,
			ClassNotFoundException {
		in.defaultReadObject();
		doReadObject(in);
	}

}
